Such a method is already known in the art, e.g. from the proposal to the FSAN-OAN (Full Service Access Network—Optical Access Network) Workgroup entitled ‘Short Slot Proposal’. This proposal is written by the authors Mark Bridger, Dan Donovan, Paul Welton, and Mike Haynes, and dated Apr. 22–23, 1997. Therein, the central station of a passive optical network (PON) with point-to-multipoint architecture regularly broadcasts so called PLOAM (Physical Layer Operation Administration and Maintenance) cells containing identifiers of the network terminals which are allowed to send a burst in the upstream timeslots of an upstream frame. The central station in the optical network of the mentioned proposal is called the OLT (Optical Line Termination), whereas the network terminals are named ONU's (Optical Network Units). The contents of such a PLOAM cell as proposed by Mark Bridger et al. is shown in a figure on page 4 of the just cited proposal. The 30 grant messages therein each contain an ONU identifier. Each ONU identified in the PLOAM cell is permitted to occupy one timeslot. By downstream broadcasting this message, all ONU's in the network become aware of the order wherein they are allowed to occupy upstream timeslots for transmission of data bursts towards the OLT. The upstream timeslots may be standard full size upstream slots with a length of 56 bytes or short slots with a length of 7 bytes. Schemes of the contents of such a short slot and such a standard full size slot are drawn in the figures on pages 2 and 3 of the proposal.
Broadcasting for each upstream timeslot an identifier of the network terminal that is allowed to send an upstream burst in it inevitably involves a high downstream bandwidth occupancy by grant messages. Especially the upstream transmission of short bursts in short timeslots requires a relatively high downstream bandwidth capacity for transfer of overhead information. In networks such as the passive optical network in the cited proposal, the length and transmit rate of PLOAM cells are fixed, and thus the bandwidth available for downstream transmission of grant messages is fixed and limited. Applying the known method for assigning timeslots to network terminals in such networks puts a severe limit on the number of timeslots within an upstream frame, irrespective of the length of these timeslots.